Ultra-large-scale integrated (ULSI) circuits may include more than one million electronic devices (e.g., transistors) that are formed on a semiconductor substrate, such as a silicon (Si) substrate, and cooperate to perform various functions within the device. Plasma etching is commonly used in the fabrication of transistors and other electronic devices. During some etching processes, one or more process gases may be provided to two or more regions, or zones, within the process chamber to etch a substrate disposed within the process chamber. In such applications, active flow controllers, such as flow sensors and flow controllers controlled based upon sensed flow, may be used to actively control the flow of the one or more gases provided to the process chamber zones. Alternatively, combinations of fixed orifices may be used to try to control the flow of the one or more gases provided to the process chamber zones.
The inventors have provided improved apparatus for controlling gas distribution.